The present invention relates to a copolyester resin composition which has good biodegradability and physical properties, and a process for preparing and/or producing the same. More particularly, the present invention have solved a problem of poor biodegradability of aromatic containing copolyester resin wherein the aromatic ingredients are incorporated to increase the physical properties of the copolyester.
The present invention relates to a copolyester resin composition and a process of preparation thereof which has good biodegradability and physical properties. The conventional aliphatic polyester completely biodegrade in the environment, but they have poor physical properties and inferior processability. To improve the physical properties and inferior processability, the aromatic group is incorporated to the aliphatic polyester, but the rate of biodegradation is greatly decreased because of the aromatic group.
The typical polyester resin used for various products including textures, fibers, moldings, formings, films, etc, is a high molecular weight aromatic polyester resin produced by the polycondensation reaction of terephthalic acid with ethylene glycol, or terephthalic acid with 1,4-butanediol. The high molecular weight polyester resin is a polymer having a number average molecular weight of over 10,000. Such aromatic polyester resins are not degradable naturally so it is a serious. worldwide of environmental concern.
Otherwise, the aliphatic polyester resins are known as being biodegradable (J. Macromol. Sci.-Chem., A23(3), pp.393-409 (1986)). They have a variety of usage in the medical and agricultural fields, and other applications are being developed.
However, the conventional aliphatic polyester resin has a low melting point and a high melt index, because of the structure of the main chain and the crystallinity thereof, and having low heat resistance and unsatisfactory mechanical properties, the usage of this polymer material has been limited. In order to utilize this aliphatic polyester resin, it should have a number average molecular weight of more than 30,000. However, it is difficult to manufacture the aliphatic polyester resins having a number average molecular weight of more than 15,000 using the conventional poly-condensation reaction system because further growth reaction is surpassed by decomposition reaction due to the poor heat stability of aliphatic polyesters.
In order to solve this problem, Korean Laid-Open Patent No. 95-758 discloses the process of preparing high molecular weighted aliphatic polyester resin having a number average molecular weight of more than 30,000, by controlling the reaction temperature, the degree of vacuum and the amount of catalyst. However, this aliphatic polyester resin has poor processability because of its low weight average molecular weight and low heat stability.
In another method, Korean Laid-Open Patent No. 95-114171 discloses the process of preparing the high molecular weighted aliphatic polyester resin by introducing monomer which containing poly(at least three)-functional groups, where the recommended functional group is hydroxy group(xe2x80x94OH) or carboxylic group(xe2x80x94COOH). According to this process, by introducing the monomer, the reaction time can be reduced and the processability of the resin can be enhanced by broadening molecular weight distribution. However, the utilization of the polyester resin thereof is very difficult because the physical property such as a tensile strength is poor due to the increased amount of low molecular weight portions. Furthermore, it is difficult to control the reaction for preparing the polyester resin, because the polyester resin easily becomes a gel type.
In yet another process for increasing the molecular weight of the aliphatic polyester resin, Korean Laid-Open Patent No. 95-25072 discloses the high molecular weighted aliphatic polyester resin produced by using isocyanate is a coupling agent reacting to an aliphaltic polyester resin having a number average molecular weight of from 15,000 to 20,000, which is produced by de-hydration reaction or de-glycol reaction of (1) an aliphatic (including, cyclic type), and (2) an aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof), and a little of (3) monomer of polyhydric alcohol or polyhydric carboxylic acid (or acid anhydride thereof). According to the application, the aliphatic polyester resin has a number average molecular weight of from 20,000 to 70,000. However, this process requires more time for the reaction which leads to the poor production yield. And the isocyanate used as a coupling agent to increase the molecular weight is harmful to the human body so it needs to be handled carefully.
In yet another process, by incorporating aromatic group to the aliphatic polyester, the physical properties have been greatly improved, but the rate of biodegradation gets very slow.
The present invention provides a copolyester resin composition which has good biodegradability and a process for preparing and/or producing the same. To improve the biodegradability and physical properties of the copolyester, the present invention applied multistage reaction step, and copolyester resin having number average molecular weight of from 30,000 to 90,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 70xc2x0 C. to 150xc2x0 C., and melt index of from 0.1 to 50 g/10 minute (190xc2x0 C., 2,160 g) is obtained. The biodegradability and physical properties of the copolyester resin of present invention has been greatly enhanced by incorporating (i) an xe2x80x9caliphatic prepolymersxe2x80x9d having number average molecular weight of from 300 to 30,000, thus the aromatic components distribute randomly and not contiguously more than 8 aromatic components in a row in the dicarboxylic acid positions of the copolyester chain. So it can be used in many practical uses including packaging film. trash bags and agricultural Film.
To solve the above mentioned problems. the present inventors applied multi-stage reaction step. The copolyester resin composition according to the present invention would be described in detail hereinafter.
In the first reaction step, the oligomer-like substances (hereinafter, referred to as xe2x80x9caliphatic prepolymersxe2x80x9d) having number average molecular weights of from 300 to 30,000 is obtained through one or a plurality of condensation, esterification and ester-exchange reaction with;
(a) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof), selected from succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid; and
(b) one or a plurality of aliphatic (including cyclic type) glycols, selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,2-octanediol, 1,8-octanediol, 1,9-nonanediol, 1,2-decanediol, 1,10-decanediol, decamethylene glycol.
Next, in the second reaction step, with the existence of (i) an xe2x80x9caliphatic prepolymersxe2x80x9d which was produced in the first reaction step, from 0.1 wt % to 30 wt %, (ii) one or a plurality of aromatic dicarboxylic acid (or an acid anhydride thereof) which containing aromatic group in the molecule, selected from dimethyl terephthalate, terephthalic acid, phthalic acid, phthalic anhydride, isophthalic acid, 4-methylphthalic acid, 4-methylphthalic anhydride, dimethyl phthalate; and (iv) one or a plurality of aliphatic (including cyclic type) glycol selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,2-octanediol, 1,8-octanediol, 1,9-nonanediol, 1,2-decanediol, 1,10-decanediol, decamethylene glycol, are added, one or a plurality of esterification and ester-exchange reaction are performed, and then produced water or methanol is extracted.
And. in the third reaction step, (iii) once or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof), selected from succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, is added thereto, and one or a plurality of esterification and ester-exchange reaction are performed. After the produced water or methanol is extracted, polymeric resin is obtained.
Finally, in the fourth reaction step, by polycondensing the polymeric resin which was obtained in the third reaction step, a copolyester resin with number average molecular weight of from 30,000 to 90,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 70xc2x0 C. to 150xc2x0 C., and melt index of from 0.1 to 50 g/10 min. (190xc2x0 C., 2,160 g) is obtained. This copolyester resin has good processability, physical properties and biodegradability.
By performing the multi-stage reaction step, the aromatic components distribute randomly and not contiguously more than 8 aromatic components in a row in the dicarboxylic acid positions of the copolyester chain.
To describe in more detail about the copolyester resin composition of this invention, in the first reaction step, (i) an xe2x80x9caliphatic prepolymersxe2x80x9d having number average molecular weight of from 300 to 30,000, is produced by performing reactions which are selected from at least one of the following reactions; condensation reaction, or an esterification reaction, or an ester-exchange reaction, with (a) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof) ingredient including succinic acid; and (b) one or a plurality of aliphatic (including cyclic type) glycol selected from at least one of 1,4-butanediol and ethylene glycol, preferably {circle around (1)} succinic acid alone; ethylene glycol alone or mixture of ethylene glycol and other glycol (C3-C10 alkylene, C4-C10 cycloalkylenc), {circle around (2)} succinic acid alone; 1,4-butanediol alone or mixture of 1,4-butanediol and other glycol (C2-C3 and C5-C10 alkylene, C4-C10 cycloalkylene), {circle around (3)} succinic acid alone or mixture of succinic acid and other dicarboxylic acid (C3-C10 alkylene, C4-C10 cycloalkylene); ethylene glycol alone, {circle around (4)} succinic acid alone or mixture of succinic acid and other dicarboxylic acid (C3-C10 alkylene, C4-C10 cycloalkylene); 1.4-butanediol alone, ),{circle around (5)} succinic acid alone or mixture of succinic acid and other dicarboxylic acid (C3-C10 alkylenc, C4-C10 cycloalkylene); ethylene glycol alone or mixture of ethylene glycol and other glycol (C3-C10 alkylene, C4-C10 cycloalkylene), {circle around (6)} succinic acid alone or mixture of succinic acid and other dicarboxylic acid (C3-C10 alkylene, C4-C10 cycloalkylene); 1,4-butanediol alone or mixture of 1,4-butanediol and other glycol (C2-C3 and C5-C10 alkylene, C4-C10 cycloalkylene)
In the second reaction step, with the existence of from 0.1 wt % to 30 wt % of (i) an xe2x80x9caliphatic prepolymersxe2x80x9d which was produced in the first reaction step, (ii) one or a plurality of aromatic dicarboxylic acid (or an acid anhydride thereof) which containing aromatic group in the molecule, including dimethyl terephthalate and terephthalic acid; and (iv) one or a plurality of aliphatic (including cyclic type) glycol selected from at least one of 1,4-butanediol and ethylene glycol, preferably {circle around (1)} dimethyl terephthalate (including terephthalic acid) alone; ethylene glycol alone or mixture of ethylene glycol and other glycol (C3-C10 alkylene, C4-C10 cycloalkylene), {circle around (2)} dimethyl terephthalate (including terephthalic acid) alone; 1,4-butanediol alone or mixture of 1,4-butanediol and other glycol (C2-C3 and C5-C10 alkylene, C4-C10 cycloalkylene), {circle around (3)} dimethyl terephthalate (including terephthalic acid) alone or mixture of dimethyl terephthalate (including terephthalic acid) and other aromatic dicarboxylic acid (or an acid anhydride thereof); ethylene glycol alone, {circle around (4)} dimethyl terephthalate (including terephthalic acid) alone or mixture of dimethyl terephthalate (including terephthalic acid) and other aromatic dicarboxylic acid (or an acid anhydride thereof); 1,4-butanediol alone, {circle around (5)} dimethyl terephthalate (including terephthalic acid) alone or mixture of dimethyl terephthalate (including terephthalic acid) and other aromatic dicarboxylic acid (or an acid anhydride thereof); ethylene glycol alone or mixture of ethylene glycol and other glycol (C3-C10 alkylene, C4-C 10 cycloalkylene), {circle around (6)} dimethyl terephthalate (including terephthalic acid) alone or mixture of dimethyl terephthalate (including terephthalic acid) and other aromatic dicarboxylic acid (or an acid anhydride thereof); 1,4-butanediol alone or mixture of 1,4-butanediol and other glycol (C2-C3 and C5-C10 alkylene, C4-C10 cycloalkylene), are added, and one or a plurality of esterification and ester-exchange reaction are performed and produced water or methanol is extracted.
The present invention provides a process for preparing and/,or producing above mentioned copolyester resin comprising four reaction steps which are described below in detail.
In the First reaction step, (i) an xe2x80x9caliphatic prepolymersxe2x80x9d having number average molecular weights of from 300 to 30,000, is obtained through one or a plurality of condensation, esterification and ester-exchange reaction, at the temperature of from 160xc2x0 to 240xc2x0 C., with; (a) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof) ingredient including succinic acid; and (b) one or a plurality of aliphatic (including cyclic type) glycol selected from at least one of 1,4-butanediol and ethylene glycol, and the produced water or the methanol is extracted. If the reaction temperature is lower than 160xc2x0 C., the produced water or methanol are not extracted. If the reaction temperature is higher than 240xc2x0 C., the reactant can be decomposed due to thermal degradation. During the reaction process, the chemical reaction is represented by the following formula (1). wherein succinic acid is employed for the (a) aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof) ingredient, and 1,4-butanediol is employed for the (b) aliphatic (including cyclic type) glycol.
HOOCxe2x80x94(CH2)2xe2x80x94COOH+HOxe2x80x94(CH2)4xe2x80x94OHxe2x86x92HOxe2x80x94[OCxe2x80x94(CH2)2xe2x80x94COOxe2x80x94(CH2)4xe2x80x94O]nxe2x80x94Hxe2x80x83xe2x80x83(I)
In which n is an integer such that the number average molecular weight of the (i) xe2x80x9caliphatic prepolymersxe2x80x9d is in the range of from 300 to 30,000.
To produce (i) an xe2x80x9caliphatic prepolymersxe2x80x9d having number average molecular weight of from 300 to 30,000, the mole ratio of (a) aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof) ingredient to (b) aliphatic (including, cyclic type) glycol ingredient is in the range of from 1.0: 1.15 to 1.0:2.0, and preferably in the range of from 1.0: 1.3 to 1.0: 1.4. If the mole ratio is less than 1.0: 1.15. the reactivity decreases and the resin becomes yellow or brown color. If the mole ratio exceeds 1.0:2.0, the production cost becomes very high.
Next, in the second reaction step, with the existence of (i) an xe2x80x9caliphatic prepolymersxe2x80x9d which was produced in the first reaction step, from 0.1 wt % to 30 wt %, (ii) one or a plurality of aromatic dicarboxylic acid (or an acid anhydride thereof) which containing aromatic group in the molecule, including dimethyl terephthalate and terephthalic acid; and (iv) one or a plurality of aliphatic (including cyclic type) glycol selected from at least one of 14-butanediol and ethylene glycol, are added, and at the temperature of from 180 to 220xc2x0 C. where the aromatic dicarboxylic acid become activated to react with the aliphatic glycol, one or a plurality of esterification and ester-exchange reaction are performed and produced water or methanol is extracted.
In the third reaction step, at the temperature of from 150xc2x0 C. to 180xc2x0 C. where the aromatic dicarboxylic acid become deactivated to react with the aliphatic glycol, (iii) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof) ingredient including succinic acid, is added, and one or a plurality of esterification and ester-exchange reaction are performed. After the produced water or methanol is extracted, polymeric resin is obtained. If the reaction temperature is lower than 150xc2x0 C., the produced water or methanol is not extracted. If the reaction temperature is higher than 180xc2x0 C., the aromatic dicarboxylic acid become activated to react with the aliphatic glycol, so the rate of biodegradation decreases. By controlling the reaction temperature in the range of from 150xc2x0 C. to 180xc2x0 C., the aromatic dicarboxylic acid cannot join the reaction process any more.
For 1.0 mole of total dicarboxylic acid (or an acid anhydride thereof) ingredient (sum of (ii) and (iii)) which are added in the second and third reaction step, the mole ratio of (iv) aliphatic (including cyclic type) glycol is in the range of from 1.15 mole to 2.0 mole, and preferably in the range of from 1.3 mole to 1.4 mole. And for 1.0 mole of total dicarboxylic acid (or an acid anhydride thereof) ingredient which is added in the second and third reaction step, the mole ratio between aromatic component to aliphatic component is in the range of from 0.3:0.7 to 0.65:0.35. If the mole ratio is less than 0.3:0.7, the copolyester resin has low melting point and poor processability. If the mole ratio is higher than 0.65:0.35, the rate of biodegradation decreases because of the aromatic component.
Finally, in the fourth reaction step, by polycondensing the polymeric resin which was obtained in the third reaction step, at the temperature of from 220xc2x0 C. to 260xc2x0 C. and 0.005xcx9c10 Torr, a copolyester resin with number average molecular weight of from 30,000 to 90,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 70xc2x0 C. to 150xc2x0 and melt index of from 0.1 to 50 g/10 min. (190xc2x0 C., 2.1 60 g) is obtained.
At the start of and/or at the end of the esterification or ester-exchange reaction in the first, second and third reaction step, and at the start of polycondensation reaction in the fourth reaction step, catalyst alone or a mixture of a plurality of catalysts can be added, wherein the amount of the catalyst(s) is preferably in the range of from 0.02 wt % to 2.0 wt % of total reactants. If the amount of catalyst employed is less than 0.02 wt %, it is very slow to extract the theoretical amount of water, methanol or glycol, or it is impossible to extract. If the amount of the catalyst employed is more than 20 wt %, the color of the product is poor even though the theoretical amount of water, methanol or glycol is easily extracted. The catalysts are selected from one or a plurality of the metallic compounds consisting Ti, Ge, Zn, Fe, Mn, Co, and Zr, preferably, an organic metallic compound consisting titanate, antimonate or tin oxide, more preferably, selected from one or a plurality of tetrabutyl titanate, calcium acetate, antimony trioxide, dibutyltin oxide, zinc acetate, antimony acetate, antimony glycolate, tetrapropyl titanate.
Additionally, at the start of and/or the end of the esterification or ester-exchange reaction in the first, second and third reaction step, and at the start of and/or the end of the polycondensation reaction in the fourth reaction step, a stabilizer can be added wherein the amount of the stabilizer employed preferably ranges from 0.02 wt % to 20 wt %. If the amount of the stabilizer used is less than 0.02 wt %, the effect of the stabilizer is not sufficient and the color of the product is yellow or brown. If the amount of the stabilizer exceeds 2.0 wt %, the time required for the reaction is extended and the product would not have high molecular weight. Therefore, the preferable amount of the stabilizer is about 0.22 wt %, and the stabilizer used is at least one or a plurality selected from phosphatic stabilizers consisting trimethyl phosphate, phosphoric acid and triphenyl phosphate.
The copolyester resin according to the present invention has good physical properties and biodegradability, so the limitations put by the conventional aliphatic polyester because of the poor tensile strength and tear strength, can be solved. The conventional aliphatic polyester completely biodegrade in the environment, but they have poor physical properties and inferior processability to apply for the packaging film, trash bags and agricultural film. And the copolyester which containing aromatic group has good physical properties, but the rate of biodegradation decreased, greatly. But the copolyester resin of the present invention has solved the above mentioned problems, and can be used in packaging film, trash bags and agricultural film.